The eyes are itchy, the nose is running and your mouth may be dry. It's hayfever.

It is the season as the deciduous trees start putting pollen into the air.

The yellow pollen that people see on puddles, in driveways and on cars is the large pollen from pine trees, says former Massey University plant biologist David Fountain.

Pollen from wattle trees had been evident since late July, and from pines since August 27.

"They'll be with us for another couple of weeks yet," he said.

Dr Fountain said the pine pollen was mildly allergenic, particularly for those who got hayfever from grass.

"At the moment, there is pollen from deciduous trees, such as hazelnuts, alders, poplars, oak and elm."

He said 10 to 20 per cent of the population was allergic to trees or grass pollen.

"Rain does wash pollen out of the air," he said.

"But dry conditions and wind mean maximum dispersal - pollen can go hundreds of kilometres.

"Most grasses flower in October and November, peaking just before Christmas - they can be a major problem."

Many people with hayfever would get antihistamine from pharmacists to relieve the symptoms.

The production of pollen depends on the time of year and the time of day, the temperature, the plant type and the altitude.

In New Zealand, from October 1, the MetService website will have the pollen forecast of high, moderate or low.

- © Fairfax NZ News